The main strength of Ancient (Classical) Athenian army was indeed hoplites; maybe not as good as Spartans', but that was their focus nonetheless. Epilektoi were elite and full-time hoplites. Since champions are elite (strongest) and full-time (cannot work), it makes perfect sense for Athenians to have hoplite champions called Epilektos.
All great ideas to differentiate them from the other hoplite civilization Spartans.
In fact, being superior sailors, Athenians would prefer less non-rowing crew and focus on manueverability for ramming. I think such a bonus makes sense when ship ramming is introduced. Nevertheless, Athenians did perform many amphibious assaults (Sicilian Expedition, campaigns against Persians), this sets them apart, and the idea of a landing unit sits well. My only concern would be: does it make sense for it to be a champion? Should Athenians have swordsmen on par with swordsmen specialists like Romans, Iberians etc.
I will propose to make Scythian Archer not a champion from the Gymnasium, but rather a mercenary either from the barracks or simply replacing the current Cretan Archers for Athenians. My justification: should Athenians rely on elite archers the way archer specialists like Kushites do, or should they have foreign mercenary archers which complement their main hoplite army? I can't imagine these guys training in the Gymnasium side by side with Epilektoi .